Conventionally, various methods of determining whether knocking (knock) is present or absent have been proposed. A knock control device for an internal combustion engine disclosed in Japanese Patent Laying-Open No. 2003-021032 includes: a knock sensor detecting knocking in an internal combustion engine; a statistical processing portion statistically processing an output signal detected by the knock sensor; a first temporal determination portion determining occurrence of knocking based on a processing result by the statistical processing portion; a second temporal determination portion determining occurrence of knocking based on a waveform shape of the output signal detected by the knock sensor; and a final determination portion finally determining occurrence of knocking based on the knock temporal determination of the first temporal determination portion and the knock temporal determination of the second temporal determination portion. When both of the first and second temporal determination portions determine that knocking has occurred, the final determination portion finally determines that knocking has occurred.
According to the knock control device disclosed by the publication, a knock temporal determination by a statistical processing program and a knock temporal determination by a waveform shape program are used, and only when both of the temporal determinations determine that knocking has occurred, it is finally determined that knocking has occurred. As a result, occurrence of knocking can precisely be determined even as to an output signal, which has been erroneously determined by a knock determination employing solely the statistical processing program or the waveform shape program.
However, in the knock control device of Japanese Patent Laying-Open No. 2003-021032, a knocking determination by statistical processing and a knock determination by waveform shape are independently performed. Accordingly, the precision of each of the determination method itself is not improved, and the problem of deterioration in the precision due to noise components is not solved in each of the determination method. Therefore, in order to precisely determine whether knocking is present or absent to thereby appropriately perform retard control or the like at the time of knocking, further improvements have still been required.